The 8051 microcontroller has two, a primary accumulator and a secondary accumulator, where the second is used by instructions only when multiplying ( MUL AB ) or dividing ( DIV AB ); the former splits the 16-bit result between the two 8-bit accumulators, whereas the latter stores the quotient on the primary accumulator A and the remainder in the secondary accumulator B.

The embedded CPU family with the largest number of total units shipped is the 8051, averaging nearly a billion units per year.

The silicon cost of an 8051 is now as low as US $ 0. 001, because some implementations use as few as 2, 200 logic gates and take 0. 0127 square millimeters of silicon.

51-FORTH is an implementation of the Forth programming language for the Intel 8051 microcontroller.

SAB-C515-LN by Infineon is based on the 8051

The Intel MCS-51 ( commonly referred to as 8051 ) is a Harvard architecture, single chip microcontroller ( µC ) series which was developed by Intel in 1980 for use in embedded systems .< ref > John Wharton: An Introduction to the Intel MCS-51 < sup > TM </ sup > Single-Chip Microcomputer Family, Application Note AP-69, May 1980, Intel Corporation .</ ref >< ref > John Wharton: Using the Intel MCS-51 < sup > TM </ sup > Boolean Processing Capabilities, Application Note AP-70, May 1980, Intel Corporation .</ ref > Intel's original versions were popular in the 1980s and early 1990s.

These registers also allowed the 8051 to quickly perform a context switch which is essential for time sensitive real-time applications.

In many engineering schools the 8051 microcontroller is used in introductory microcontroller courses.

Program memory is read-only, though some variants of the 8051 use on-chip flash memory and provide a method of re-programming the memory in-system or in-application.

Because the 8051 is an accumulator-based architecture, all arithmetic operations must use the accumulator, e. g. ADD A, 020h will add the value in memory location 0x20 in the internal RAM to the accumulator.

An 8051 chip could be sold as a ROM-less 8031, as the 8051's internal ROM is disabled by the normal state of the EA pin in an 8031-based design.

The AVR Instruction Set is more orthogonal than those of most eight-bit microcontrollers, in particular the 8051 clones and PIC microcontrollers with which AVR competes today.

97 is a non-trivial factor of 8051.

* Also, a free compiler, Turbo51, is available for producing code for Intel 8051 chips.

The card is based on an 8051 processor with 3DES / AES crypto accelerator, making very fast transactions possible.

Other high level languages such as Forth, BASIC, Pascal / Object Pascal, PL / M and Modula-2 are available for the 8051, but they are less widely used than C and assembly.

Enhanced 8051 cores are now commonly used which run at six, four, two, or even one clock per machine cycle, and have clock frequencies of up to 100 MHz, and are thus capable of an even greater number of instructions per second.

This same feature was used to emulate the 8051 keyboard controller, serial port and numerous other I / O functions.

The 8052 and 8032 are largely considered to be obsolete because these features and more are included in nearly all modern 8051 based microcontrollers.

Designers use 8051 silicon IP cores, because of the smaller size, and lower power, compared to 32 bit processors like ARM M series, MIPS and BA22.

Based on the Intel 8051 core, the AT89 series remains very popular as general purpose microcontrollers, due to their industry standard instruction set, and low unit cost.

Historically almost all early computers were accumulator machines ; and many microcontrollers still popular as of 2010 ( such as the 68HC12, the PICmicro, the 8051 and several others ) are basically accumulator machines.

Many microcontrollers are so quirky that they effectively require their own non-standard dialects of C, such as SDCC for the 8051, which prevent using standard tools ( such as code libraries or static analysis tools ) even for code unrelated to hardware features.

A long but still not exhaustive list of common architectures are: 65816, 65C02, 68HC08, 68HC11, 68k, 78K0R / 78K0, 8051, ARM, AVR, AVR32, Blackfin, C167, Coldfire, COP8, Cortus APS3, eZ8, eZ80, FR-V, H8, HT48, M16C, M32C, MIPS, MSP430, PIC, PowerPC, R8C, RL78, SHARC, SPARC, ST6, SuperH, TLCS-47, TLCS-870, TLCS-900, TriCore, V850, x86, XE8000, Z80, AsAP and others.

The 8051 architecture provides many functions ( CPU, RAM, ROM, I / O, interrupt logic, timer, etc.

One particularly useful feature of the 8051 core was the inclusion of a boolean processing engine which allows bit-level boolean logic operations to be carried out directly and efficiently on select internal registers and select RAM locations.

With a single instruction the 8051 can switch register banks as opposed to the time consuming task of transferring the critical registers to the stack or designated RAM locations.

The original 8051 core ran at 12 clock cycles per machine cycle, with most instructions executing in one or two machine cycles.

With a 12 MHz clock frequency, the 8051 could thus execute 1 million one-cycle instructions per second or 500, 000 two-cycle instructions per second.

Features of the modern 8051 include built-in reset timers with brown-out detection, on-chip oscillators, self-programmable Flash ROM program memory, built-in external RAM, extra internal program storage, bootloader code in ROM, EEPROM non-volatile data storage, I²C, SPI, and USB host interfaces, CAN or LIN bus, PWM generators, analog comparators, A / D and D / A converters, RTCs, extra counters and timers, in-circuit debugging facilities, more interrupt sources, and extra power saving modes.

Many variants of the 8051 include the standard 256 bytes of IRAM plus a few KB of XRAM on the chip.

There are various high-level programming language compilers for the 8051.

Several C compilers are available for the 8051, most of which feature extensions that allow the programmer to specify where each variable should be stored in its six types of memory, and provide access to 8051 specific hardware features such as the multiple register banks and bit manipulation instructions.

The existence of a community is a state of mind -- a conviction that goals and values are widely shared, that effective communication is possible, that mutual trust is reasonably assured.

Of the handful of painters that Austria has produced in the 20th century, only one, Oskar Kokoschka, is widely known in the U.S..

What they should recognize is that children who have been placed in one of these groups on a narrow academic basis still differ widely in attributes that influence success, and that they still must be treated as individuals.

But to return to the main line of our inquiry, it is doubtful that Utopia is still widely read because More was medieval or even because he was a martyr -- indeed, it is likely that these days many who read Utopia with interest do not even know that its author was a martyr.

Utopia is still widely read because in a sense More stood on the margin of modernity.

Every few days, in the early morning, as the work progressed, twenty men would appear to push it ahead and to shift the plank foundation that distributed its weight widely on the Rotunda pavement, supported as it is by ancient brick vaulting.

Because agricultural activities are seasonal and the areas of production and harvest of many foods are widely scattered geographically, and because of the high cost of transporting bulk food items any substantial distance to a central processing location, the use of large central processing stations, where low-cost radiation facilities approaching the megawatt range might be utilized, is inherently impracticable.

The suburban high school, it is worth noting, also is not a widely comprehensive high school because of the absence of vocational programs.

Corruption is hardly a recent development in the city and state that were widely identified as the locale of Edwin O'Connor's novel, `` The Last Hurrah ''.

There is nothing in the whole range of human experience more widely known and universally felt than spirit.

The English saints are widely venerated, quite naturally, and now there is great hope that the Forty Martyrs and Cardinal Newman will soon be canonized.

The average overall albedo of Earth, its planetary albedo, is 30 to 35 %, because of the covering by clouds, but varies widely locally across the surface, depending on the geological and environmental features.

Famous novelists of the 20th century include Mohammed Dib, Albert Camus, Kateb Yacine and Ahlam Mosteghanemi while Assia Djebar is widely translated.

Among the proposed etymologies is the Hurrian and Hittite divinity, Aplu, who was widely invoked during the " plague years ".

The most widely spoken Afroasiatic language is Arabic ( including all its colloquial varieties ), with 230 million native speakers, spoken mostly in the Middle East and North Africa.

The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks in Asia, Africa, and elsewhere.

The Brønsted-Lowry definition is the most widely used definition ; unless otherwise specified acid-base reactions are assumed to involve the transfer of a proton ( H < sup >+</ sup >) from an acid to a base.

This essay is widely held to be one of the greatest examples of sustained irony in the history of the English language.

Cyrillic is one of the most widely used modern alphabetic scripts, and is notable for its use in Slavic languages and also for other languages within the former Soviet Union.